Some motor vehicle control systems require angular position sensors that need only sense partial angular motion of one part relative to another part, e.g., less than plus or minus ninety degrees. Shaped magnets have been used in conjunction with magnetic field sensors in order to provide non-contact angular position sensors that sense partial angular motion. Angular position sensors utilizing rotating magnets sensed by stationary magnet field sensors typically produce a sinusoidal or pseudo-sinusoidal output signal. These signals may somewhat approximate a linear output signal at least over some limited angular range. Also, resistance-strip position sensors have been widely used to determine the position of a moving part relative to a corresponding stationary part. Such sensors can have reliability problems due to the susceptibility of the resistance-strips to premature wear. Also, the vibration of contact brushes along the resistance-strips may cause unacceptable electrical noise in the output signals.
Current magnetic, rotary position sensors, such as a Hall-effect type sensor utilize a wide variety of magnetic configurations to achieve the required characteristics of the raw magnetic signal. Most configurations employed minimize or avoid the non-linear effect caused by free-space, or air, on the flux distribution, i.e., magnitude and direction, surrounding the magnetic source. One way of minimizing or avoiding this undesired effect is by utilizing magnetic flux concentrators that direct flux lines to desired locations. Depending on the application, these concentrators may be of common ferromagnetic material or may require the use of other material, such as Silicon-Iron, to achieve desired characteristics such as low hysterisis, for example. The number of flux concentrator pieces may double if the application requires sensor redundancy.
When flux concentrators are not used, the geometrical shapes of the magnetic sources may become complex. Also, the geometrical shapes of the concentrators themselves are often complex. As with any other component, geometrical complexity increases the cost associated to produce such component and obviously drives the total component and manufacturing costs of the respective sensor assembly. Those sensors utilizing concentrators and requiring low hysterisis are typically the most expensive because of the special material required. Typically, the wider the application ranges of rotation, the higher the cost of the sensor system.